Z is for Zirconia

Most of you know this as synthetic diamond and probably a few of you have some of these gems at home.  They are sparkly and beautiful and can be almost any color.

It may surprise you to know that the main use of zirconia is in the production of ceramics as in dentistry.  It’s used in reconstruction, such as crowns or bridges.  Stabilized zirconia is used in oxygen sensors.  It also has potential applications as an insulator in transistors.

A brilliant cut cubic zirconia - pic courtesy of Wikipedia

When used in jewelry it has a high index of refraction and the same crystal structure as diamond.  It’s very difficult to determine the difference of a diamond and zirconia by visual testing alone.  A thermal conductivity test needs to be performed.  Diamond is a good thermal conductor where zirconia isn’t.

T is for Turquoise

Turquoise - pic courtesy of Wikipedia

Turquoise is an opaque green to blue mineral.  This mineral is a hydrated phosphate of copper and aluminum.  It’s been known by many names but ended up with the name turquoise because its arrival in Europe in the 17^th century was through Turkey from mines in Persia.

Turquoise is typically found in arid regions, suggesting climate plays a big part in its formation.

Turquoise - pics courtesy of Wikipedia

Turquoise was among the first gems ever mined.  The mining is done by hand in small scale operations.  It’s often discovered as a byproduct of large scale copper mining in the United States.  Copper mines are also found in Iran and on the Sanai Peninsula.  The southwest United States is a significant source of turquoise.  Sometimes in an attempt to meet demand, turquoise is treated or enhanced.  Sometimes these treatments also include  waxing or dyeing.

Even though turquoise was used in ancient times, it didn’t become significant until the 14^th century following a decline in the Roman Catholic Churches influence which allowed the stone to be used in secular jewelry.

Turquoise - pic courtesy of Wikipedia

Turquoise was thought to change color with the wearers health and protect him or her from untoward forces.

Turquoise was widely used by the Aztecs, Pueblo, Navajo and Apache tribes.  They cherished turquoise as amulets.

Turquoise - pic courtesy of Wikipedia

Turquoise is fragile and sensitive to solvents and even perfume.  Care must be taken so as to avoid contact with body lotion, sunscreen and cosmetics.  It’s also best to keep turquoise away from direct sunlight, as it can fade with prolonged sun exposure.

S is for Sapphire

Sapphire is a precious gemstone of the mineral corundum, an aluminum oxide.  Sapphire is typically blue, but natural “fancy” sapphires can be yellow, purple, orange and green, or “parti sapphires,” which are two or more of these colors.  The only color sapphire can’t be is red because red corundums are rubies.  The variety in color is from trace amounts of iron, titanium, chromium, copper, or magnesium.

This beauty is the Logan Sapphire and it weighs 423 carats - Wikipedia

Sapphires are usually cut and polished into gems and worn as jewelry although they can also be used in wristwatch crystals, high-durability windows and thin electronic wafers among other things.  Sapphire, like ruby, is also a 9.0 on Mohs scale of hardness.

A cut and polished sapphire gemstone - Wikipedia

Sapphire is graded like other gemstones, as mentioned before, by color, cut, clarity and carat weight.  The color of gemstones can be described in terms of hue, saturation and tone.  Hue is the “color” of the gemstone.  Saturation is brightness of the hue and tone is the lightness and darkness of the hue.

A beautiful teardrop cut sapphire - Wikipedia

Green or gray lessens the hue considerably and also the value.  Ideally it’s best to have violet or purple contribute to the intensity of the blue color of sapphires.

Here’s an interesting tidbit about parti sapphires.  Australia is the largest source of particolored sapphires.  These aren’t typically used in jewelry so are relatively unknown.  Particolored sapphires cannot be created synthetically and only occur naturally.

A padparadscha sapphire - Wikipedia

Naturally formed pink-orange corundum is very rare.  This type of sapphire is called Padparadscha.  This name comes from the name for the lotus flower as this is much the same color.  These stones are often from Sri Lanka.  Orange gems are often higher in price than the highest quality blue sapphire.  Because of heat treatment called lattice diffusion, more of these orange gems are being seen in the marketplace, but the naturally occurring ones are the most valuable.

Star sapphire - Wikipedia

The star sapphire exhibits a star pattern when viewed from a single overhead light source.  This star is due to rutile inclusions in the stone when it was formed.  As discussed earlier, rutile is titanium dioxide.  These gems are generally cut into cabochons (flat on the bottom) and mounted that way with the star facing outward.  The red stones like this are called “star rubies.”

Sapphire is the birthstone for September and also the gem for a forty-fifth anniversary.

R is for Ruby

Ruby from Wikipedia

Ruby is a pink to deep red gemstone from the mineral corundum.  The red color is caused by chromium.  Ruby is one of the original cardinal gems, considered precious above other gemstones.  Other gems falling into this category are sapphire, emerald, amethyst and diamond.

Natural occurring ruby - Wikipedia

The quality and price of ruby is determined by its color, cut, clarity and weight, just like the other precious gemstones listed above.  Blood-red is the most valuable color for rubies.  The stone should have good clarity too, but not be too perfect.  Inclusions are trapped inside gems when they’re formed.  Looking at one that’s perfect could indicate it’s been treated because all rubies have needle-like inclusions of rutile, a mineral that’s primarily titanium oxide. 

Cut red ruby gemstone - Wikipedia

Cut pink ruby gemstone - Wikipedia

Other than diamond and moissanite, a naturally occurring silicon carbide used in industry, ruby is the hardest gem with a reading of 9.0 on the Mohs scale of hardness.  This scale was invented in 1812 by German geologist and mineralogist, Friedrich Mohs.

Victorian ruby and diamond brooch - Wikipedia

The world’s most valuable ruby is the Sunrise Ruby, which sold in auction by Sotheby’s, in May 2015 in Geneva Switzerland, for a whopping 30.42 million US dollars.

Ruby is the birthstone for July.

M is for Malachite

Malachite is a beautiful stone with layers of light and dark green.  This makes it easy to recognize.  The lines can be straight, curvy or wiggly. 

Malachite, isn't this beautiful?

Malachite often results from the weathering of copper ores.  It is typically associated with copper deposits around limestone.  Sometimes it’s found as stalactites in caves.  Wouldn’t that be an amazing sight?

This malachite is from Arizona 

Malachite is found worldwide.  Arizona is the most notable place in the US.

Malachite specimens

Malachite can be used for ornaments, furniture and jewelry.  There are large vases in museums.

Malachite - this vase is in Hermitage Museum in St. Petersburg

When I lived in Alaska in the 1970’s, we sold malachite and other gemstones, such as turquoise, in the leather store I worked in.  We had lots of items that used stone embellishments.  I still have a purse I made in the leather shop there and it has a drilled malachite closure.

Photos courtesy of Wikipedia and a gemstone site in the UK

G is for Geodes

I was going to write about gold here, but this is more interesting and there are some facts here that I bet you’ll be surprised about.

Unopened geode - see how plain this is

This is a geode sliced open.  Sorry this pic is in black and white

Geodes are agates that got their name from “achates” because the first one was found near the river Achates in Sicily.  Agates come in a wide variety of colors and patterns.  One must be careful buying them because this stone is easy to dye and the bright, gaudy ones aren’t natural colors.

A geode slice

But how they form is the really cool thing about agates.  They occur as a cavity filling in lava.  If a bubble of gas forms in the lava when it hardens this bubble fills up with silicates.  This is called geode.  You can buy whole geodes, which look dull and like a lump of rock but once opened they glisten with quartz crystals, which can be in many beautiful colors.  It’s truly a feast for the eyes that something so stunning can be on the inside of something so plain and ordinary. 

Here are more sliced geodes

I’m sure many of you have seen these around in souvenir shops, or at gem fairs.  They are strikingly gorgeous and make good bookends, or a conversation piece to sit on a shelf.

And look at this one.  Isn't it pretty?

You can also buy flat “slices” of geodes, which show patterns to their best effect.  When the geode fills up sometimes it hardens in layers of different colors.  If there’s a gap more quartz crystals may grow.  These flat pieces make excellent jewelry.

E is for Emerald

This was covered in B under beryl so I had to do some more digging to find more info on this one.

Impurities in beryl cause different colors that create different gemstones.  Beryl is a colorless mineral, but when chromium is added it becomes green and emerald.  Beryl with iron added becomes blue and is then aquamarine.

Isn't this beautiful?  This is from Musa Columbia

Emeralds are hard, but inclusions (flaws) can cause them to crack.  Sometimes gemstones are heated to increase color and clarity.  Of course caution has to be used during the heating process.  

I found this fact interesting.  Emeralds with fissures are treated with wax or oil that is colored.  This creates a stone with more clarity thus making it more desirable.

Raw uncut, unpolished emerald

Gemstones can be natural or lab created (synthetic).  It’s almost impossible to tell the difference between the two.  But synthetic gemstones are usually more perfect in color and clarity because they weren’t created by nature where impurities exist.

Most of the largest emeralds are in museums or private collections.

Most of the info and photos are from Wikipedia, GIA and Gem Select websites.